Fixed inconsistent line endings in text files

Fixed inconsistent line endings in text files

I found some .robot files with Microsoft-style line endings
which are removed by the "tidy" tool, creating unwanted
noise in the form of making it appear that every line was
changed.

To make sure this is not going to happen anymore a
.gitattributes file was added that declares the .robot files
and a large bunch of other files to be text and specifies
that the line endings shall be normalized using the "auto"
algorithm unless the user configures his Git differently.

Change-Id: I653c691759aad7baccea2e6d4266254a072cbfe1
Signed-off-by: Jozef Behran <jbehran@cisco.com>